Protective coating materials for electrochromic devices

ABSTRACT

The present invention is directed to a polymeric coating material used to protect electrochromic devices from environmental and mechanical damage. The protective polymeric coating material in the present invention are physically, chemically and optically compatible with the electrochromic cell layers. The polymeric coating materials in the present invention are polymers having generic polymer back-bones selected from the group consisting of polyimides, polybenzimidazoles, polybenzothiazoles, polybenzoxazoles, poly(phenylene ethers), polyquinolines, polycarbonates and polysulfones.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention is directed to polymeric materials used to formprotective coatings on electrochromic devices. The present invention isalso directed to a process for preparing electrochromic devices having aprotective polymeric coating thereon.

2. The Relevant Technology

Electrochromic devices are optical devices typically composed of thinlayers of inorganic oxides that change color in response to an appliedvoltage. Electrochromic devices have many useful applications, such asintentionally darkening windows, mirrors, eyeglasses, filters andelectro-optical devices. A problem with electrochromic devices, however,is that electrochromic devices lack the long term durability to bepractically useful.

Electrochromic devices lack the structural and chemical durability tohave any viable commercial application. Even the slightest physicalcontact can damage an electrochromic structure and render theelectrochromic device unusable. Furthermore, any scratch or otherblemish on the surface of the electrochromic device can adversely effectthe optical qualities of the device. In short, electrochromic devicesare exposed to physical contact that destroys, or significantly shortensthe lifetime of electrochromic devices.

Similarly, electrochromic devices have a delicate chemical make up thatis easily altered by exposure to reactive substances, such as moisture,oxygen, cleaning solutions and other contaminants. Any variation in thechemical nature of the electrochromic layers, whether from the evolutionof necessary elements from the device, or the invasion of reactiveelements into the device, adversely effects, or destroys, the properfunctioning of the electrochromic device. Hence, for the electrochromicdevice to be economically viable, it is vital that any physical orchemical contact with the electrochromic device be greatly reduced orcompletely avoided.

In an attempt to make electrochromic devices commercially viable, manypeople have tried to increase the mechanical and environmentaldurability of electrochromic devices by coating the electrochromicdevices with polymers, reaction curing-type resins, adhesive resins andother various materials. While many of these coating materials have beeneffective barriers to environmental or mechanical elements, none of theproposed coatings have provided complete protection from bothenvironmental and mechanical damage. For instance, many polymericmaterials form effective environmental or chemical barriers, but aremuch less effective in protecting electrochromic devices againstmechanical impact, such as scratching, handling, or other contact(Japanese Application No. 58-91431(A); Baucke et al., U.S. Pat. No.4,465,339; Ganglier et al., U.S. Pat. No. 4,392,720; Bissar et al., U.S.Pat. No. 4,227,779; and Amano, U.S. Pat. No. 4,403,831). Similarly,coating materials that form effective mechanical barriers are commonlyporous and, thus, do not provide adequate environmental or chemicalprotection for electrochromic devices.

To provide an environmental and mechanical barrier for electrochromiccells, Agrawal U.S. Pat. No. 4,852,979, discloses the use of two layersof protective materials, one layer immediately adjacent to theelectrochromic cell that protects the cell from mechanical damage and anouter layer covering the entire area of the electrochromic cell,including the mechanical barrier, that protects the cell from reactiveelements, such as moisture and oxygen. The combination of these twolayers provides a coating that effectively protects the electrochromicdevice from mechanical and electrical damage.

Unfortunately, the use of two layers is time consuming and expensive.Furthermore, as mentioned above, electrochromic devices are opticaldevices and any coating added to the electrochromic device must notadversely effect the optical characteristics of the device. Therefore,the coatings must have a specific refractive index, optical emissivity,thermal expansion coefficient, etc. The greater the number of layersadded to the electrochromic device, the greater the possibility that theoptical qualities will be affected. A further drawback of the process inAgrawal is that the materials used to form the protective layers cannotbe exposed to temperatures greater than 65° C. during processing. Thisseverely limits the curing process and coating materials that may beused in coating formation.

From the foregoing, it is readily apparent that there is a need for acoating material that can be used to protect electrochromic devices fromenvironmental as well as mechanical damage while maintaining the opticalqualities of the electrochromic device. Furthermore, it is clear thatthere is a need for an efficient process for coating electrochromicdevices.

SUMMARY AND OBJECTS OF THE INVENTION

It is, therefore, an object of the present invention to provide aprotective coating material that protects sensitive devices from bothenvironmental and mechanical damage.

It is another object of the present invention to provide a protectivecoating material that is physically and chemically compatible withelectrochromic devices.

It is also an object of the present invention to provide a protectivecoating material that is compatible with the optical characteristics ofelectrochromic devices.

It is a further object of the present invention to provide simpleprocess for applying a protective coating on an electrochromic device.

To achieve the foregoing objects, and in accordance with the inventionas embodied and broadly described herein, the present invention isdirected to a polymeric coating material that effectively protectsdelicate devices from environmental and mechanical damage. The polymericcoating material in the present invention is physically, chemically andoptically compatible with the electrochromic cell layers.

In a preferred embodiment of the present invention, an electrochromicdevice comprises an electrochromic cell and a coating on theelectrochromic cell, wherein the coating comprises a polymer having thegeneral formula selected from the group consisting of: ##STR1## whereinAr is selected from the group consisting of: ##STR2## wherein Ar¹ isselected from the group consisting of: ##STR3## wherein n is between 1and 10; wherein X is 0 or 1;

wherein R is selected from the group consisting of H, CF₃, C_(n)H_(2n+1), OC_(n) H_(2n+1) and mixtures thereof; and

wherein R¹ is selected from the group consisting of H, CF₃, C_(n)H_(2n+1), OC_(n) H_(2n+1), -phenyl, fluorenyl, naphtalenyl and mixturesthereof.

In a more preferred embodiment of the present invention, the coatingmaterial is a polymer selected from the group consisting of a polymerhaving the recurring structural unit[Poly[2,5-benzoxazolediyl[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]-5,2-benzoxazolediyl-4,4'-phenylether]]n';[α-[1,4-Biphenylyl]-ω-[4-[[4-(4-phenylphenoxy)phenyl]phenylphosphinyl]phenoxy]-poly[oxy-1,4-phenylene(phenylphosphinylidene)-1,4-phenyleneoxy-1,4-phenylene-9H-fluoren-9-ylidene-1,4-phenylene]]n';and[α-[1,4-Biphenylyl]-ω-[4-[[4-(4-phenylphenoxy)phenyl]phenylphosphinyl]phenoxy]-poly[oxy-1,4-phenylene(phenylphosphinylidene)-1,4-phenyleneoxy-1,4-phenylene[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]-1,4-phenylene]]n';wherein n' is an integer.

The present invention also provides methods of manufacturing anelectrochromic device comprising an electrochromic cell having aprotective coating thereon. In a preferred embodiment the methodcomprises forming an electrochromic cell on a supportive substrate, suchas glass or other plastic or polymeric structure; coating theelectrochromic cell with a polymeric solution which when dried will bechemically inert, have high optical qualities and be thermally stable;and annealing the coating by heating the electrochromic device to atemperature above 65° C.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and other advantagesand objects of the invention are obtained, a more particular descriptionof the invention briefly described above will be rendered by referenceto a specific embodiment thereof which is illustrated in the appendeddrawings. Understanding that these drawings depict only a typicalembodiment of the invention and are not therefore to be considered to belimiting of its scope, the invention will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 illustrates a cross-sectional view of a prior art electrochromicdevice.

FIG. 2 illustrates a cross-sectional view of an electrochromic devicecomprising an electrochromic cell on a supportive substrate, wherein theelectrochromic device comprises a protective coating on theelectrochromic cell.

FIG. 3 is a graph illustrating differences in the long term performancebetween a prior art electrochromic device and an electrochromic deviceprotected by a polymeric sealing layer produced according to the presentinvention.

FIG. 4a illustrates the optical deterioration of an unsealed transparentelectrochromic device operated at 85° C.

FIG. 4b illustrates the absence of any optical deterioration in a sealedtransparent electrochromic device having operated at 85° C. (the deviceis presented in its bleached state).

FIGS. 5a-5h contain representations of the generic polymer structuresuseful as coating materials for electrochromic devices.

FIGS. 6a-6c contain representations of specific polymer structuresuseful as coating materials for electrochromic devices.

FIG. 7 illustrates a cross-sectional view of a packaged electrochromicdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to polymeric materials used to formprotective coatings on electrochromic devices. The present invention isalso directed to a process for preparing electrochromic devices having aprotective polymeric coating thereon. As used herein electrochromicdevices include, but are not limited to, transparent electrochromicdevices and electrochromic mirrors.

Electrochromic devices have many useful applications, such asarchitectural windows, sunglasses, mirrors and electro-optic displays.However, electrochromic devices lack the long-term durability to haveany commercially viable application.

To increase their durability, electrochromic devices are typicallycoated with protective coatings that insulate the electrochromic cellfrom its external environment. Although many different coatingmaterials, including organic and inorganic materials have been used asprotective coatings for electrochromic cells, none of these coatingsprotect electrochromic devices from both environmental and mechanicaldamage.

In an attempt to provide adequate protection from external elements,multiple layers of differing materials have been applied toelectrochromic devices. In addition to being both time consuming andexpensive, it is difficult to maintain the optical quality ofelectrochromic devices when multiple layers of differing materials areapplied to the surface of the electrochromic device. This problem iscompounded by other specific requirements necessary for electrochromicdevices. For instance, the refractive index of the layers must match therefractive index of the electrochromic device, the thermal expansioncoefficients of all the materials should be close to the thermalexpansion coefficient of the electrochromic structure to avoid anymechanical stress being applied to the delicate electrochromic device,the materials must be chemically inert so that the materials do notreact with the inorganic oxide layers of the electrochromic device, aswell as many other necessary requirements. The more materials and themore layers that are added to the electrochromic device, the greater thechance that the materials will adversely affect the electrochromicdevice. Unfortunately, a single coating material that protects theelectrochromic cell from its surroundings, both mechanically andenvironmentally, as well as having all the other properties necessaryfor the proper functioning of electrochromic devices is not known.

It is a feature of the present invention to provide a material forcoating electrochromic devices, that protects electrochromic devicesfrom their surroundings. In addition to its protective function, coatingmaterials preferably have a number of other qualities important to theproper functioning of electrochromic devices.

In a preferred embodiment, in addition to coating materials protectingelectrochromic devices from environmental and mechanical damage, coatingmaterials should also possess a unique combination of properties topreserve the delicate physical and chemical make up of electrochromicdevices. These properties include:

(a) being chemically inert, so that the coating does not adverselyaffect the layers of the electrochromic cell or react upon prolongedexposure to ultraviolet light;

(b) having high optical quality such that light does not scatter as itpasses through the coating layer and so that the refractive index of thecoating can be matched to the refractive index of the electrochromiccell;

(c) being thermally stable, such that the coating is stable over a broadrange of temperatures (at least -50° C. to 150° C.) and that the thermalexpansion coefficient of the coating will not result in any unduemechanical strain as the coating cures;

(d) having a low emissivity, i.e., having a very low absorption in theinfrared region, so that when the electrochromic device is used as awindow, the protective layer will not absorb heat;

(e) being soluble in organic solvents that are suitable for coatingelectrochromic devices;

(f) having a strong adhesion to the electrochromic device;

(g) having a low gas permeability; and

(h) having a high transmission in the visible region.

In accordance with the present invention, it has been discovered thatpolymeric materials having the following generic polymeric back-bonesstructures are particularly useful as electrochromic devices: ##STR4##wherein Ar is selected from the group consisting of: ##STR5## whereinAr¹ is selected from the group consisting of: ##STR6## wherein n isbetween 1 and 10; wherein X is 0 or 1;

wherein R is selected from the group consisting of H, CF₃, C_(n)H_(2n+1), OC_(n) H_(2n+1) and mixtures thereof; and

wherein R¹ is selected from the group consisting of H, CF₃, C_(n) H_(2n)+1, OC_(n) H_(2n+1), -phenyl, fluorenyl, naphtalenyl and mixturesthereof.

By modifying these generic polymeric chains with differing combinationsof the appropriate functional groups listed above, a large number ofeffective polymeric materials can be formed having the above-mentioneddesirable qualities.

More specifically, in a preferred embodiment of the present invention,specific polymeric coating materials that have proven to be particularlyuseful in coating electrochromic devices include polymers having thefollowing recurring structural units: ##STR7##

Referring now to FIG. 2 of the drawings which illustrates across-section of a preferred solid state electrochromic device 50 thatis completely protected from the external environment by a protectivecoating 46. The electrochromic cell 52 is a proton based solid stateelectrochromic structure comprising a first electrical conducting layer30, such as indium tin oxide, having either an electrochromic layer or acounter electrode layer 32 formed thereon. Layer 34 formed on layer 32is an ion conducting layer which allows the ions to migrate between theelectrochromic layer and the counter electrode layer. Layer 36 locatedon the ion conducting layer is either a counter electrode layer or anelectrochromic layer depending on layer 32. For example, if layer 32 isan electrochromic layer, layer 36 is either a counter electrode layer oran electrochromic layer. If layer 32 is a counter electrode layer,however, layer 36 is an electrochromic layer. A second electricalconducting layer 38 is formed on layer 36. The electrochromic cell isformed using any known technique for depositing layers 30, 32, 34, 36and 38, including, but not limited to vacuum deposition, sputtering,evaporation, solution dipping, spinning, spraying and the like.

A voltage is applied to the electrochromic device by a voltage meanswhich includes any type of electrical connection. Bus bars 40 and 42 areexamples of voltage means that provide a voltage through the layers ofelectrochromic device 50. In the preferred embodiment, illustrated inFIG. 2, first bus bar 40 is positioned such that it contacts firstelectrical conducting layer 30 and second bus bar 42 is positioned suchthat it contacts second electrical conducting layer 38. Theelectrochromic cell 52 is typically formed on a supportive substratestructure 44, such as glass. Protective coating 46 is formed on theelectrochromic cell so that the protective coating encompasses at leastlayers 32, 34, and 36. As illustrated in FIG. 2, bus bar 40 and 42 areexposed to the external environment so that an electrical connection canbe made to the electrochromic cell 52.

Protective coating 46 provides excellent optical quality forelectrochromic device 50 while functioning as an efficient barrier towater, oxygen, chemicals, high temperatures and other environmentalelements and contaminants. In addition to preventing environmentalcontaminants from contacting the electrochromic cell layers, theprotective coating also traps and contains necessary materials withinthe electrochromic cell, such as an optimum amount of moisture. Byacting as a barrier to the external environment and by trapping thenecessary materials within the cell, the protective coating preventspremature deterioration of the electrochromic device by preserving thecharge capacity at the counter electrode layer of the electrochromiccell. Coating layer 46 also allows electrochromic device 50 to becleaned using common organic solvents or water-based detergents and alsoacts as an efficient barrier to mechanical damage, absorbing the impactfrom transporting, handling, or other external contact.

Polymers within the scope of the present invention are preferablyapplied to the electrochromic cell in a solution of the polymer in asuitable organic solvent. The polymeric material can be present in thesolution in any amount that will form a coating on the electrochromicdevice, but is preferably present in amount between about 0.2% to about10% by weight of the polymer in a suitable organic solvent, and mostpreferably between about 0.5% to about 10% by weight.

Any suitable organic solvent can be used to dissolve the solution in thecoating process. The solvent should not, however, have a boiling pointso low as to cause deterioration in the optical quality and mechanicalresilience of electrochromic devices provided with the protective layer.Additionally, it is important that the solvents not have a boiling pointso high that it is difficult to remove after the protective coating hasbeen applied. Extended periods of exposure to very high dryingtemperatures when high boiling point solvents are used may damage theelectrochromic devices. Furthermore, solvents having reactive, highlypolar functional groups should be avoided during the coating processbecause these functional groups tend to interact with the functionalgroups present on the polymeric structures and are, thus, difficult toremove. If these polar solvents are not entirely removed from theprotective coating layer, the reactive, polar functional groups tend toreact with and destroy the inorganic oxide layers of the electrochromiccell. Moreover, it is important that none of the organic solvent remainstrapped under the protective coating layer because any remaining organicsolvent will taint the electrochromic device and the polymer coating.

In a preferred embodiment, the organic solvents used to form thepolymeric solutions include, but are not limited to, toluene, xylenes,chlorobenzene, ortho-dichlorobenzene, cyclopentanone, cyclohaxanone, andmixtures thereof. Alkyl and alkoxy groups can be added to the polymericback-bone structure to make the polymeric coating materials more solublein the organic solvents.

After the polymer is dissolved in an appropriate amount of the organicsolvent, the polymer solution is preferably filtered to remove anymicroparticles or other impurities that may affect the depositionprocess. The polymeric solution should then be out-gassed under lowpressures to remove any micro-bubbles and dissolved gasses.

The electrochromic cell is mounted into the coating equipment, thecoating parameters are set for properties such as the polymeric coatthickness, and the polymeric coating material is deposited on theelectrochromic cell. The protective coating can be applied to thesurface of the electrochromic cell using any suitable depositiontechnique known in the art, including, but not limited to, spin coating,dipping, spraying, roll-coating and extrusion, so that the protectivecoating is applied in an uniform manner, free of pin holes or any otherdefects. Defects such as non-uniformities and pin holes at the interfaceof the protective coating and the electrochromic cell result in opticalinterference effects of the electrochromic device. When the polymericcoating material has dried on the electrochromic cell the coating willbe chemically inert, have high optical qualities and be thermallystable.

In a preferred embodiment, the coating step is performed in anenvironment having a reduced level of humidity and a reduced level ofoxygen, so that no moisture, oxygen or other chemical is captured underthe protective coating layer. An inert atmosphere may be used to reducethe moisture and oxygen content during the deposition process. Dependingon the polymer used to form the protective coating, it may be necessaryto process the polymeric coating layers under extremely dry conditionsto form protective coating layers having the desired qualities.

Once applied to the electrochromic cell, the polymeric coating materialsare exposed to a high temperature annealing processes. The annealingprocess is preferably performed by heating the electrochromic device toa temperature above about 65° C., and most preferably in a range betweenabout 75° C. and about 250° C. Elevated temperatures during theannealing process accelerate the drying process of the freshly coatedprotective material and allow the polymeric coating material to reachits most stable structure and configuration both chemically andphysically in a short period of time. The particular temperature used inthe annealing process is dependent on the chemical structure of thepolymeric material being used. It is, however, important to avoidexposure of the coated electrochromic device to thermal shock during theannealing process.

It is preferable to keep the relative humidity during the annealingprocess as low as possible. A relative humidity above 45% during theannealing process may detrimentally affect the performance of theprotective coating layer. Once deposited, dried and annealed, theambient humidity does not affect the protective coating layer.

After the annealing process, the polymeric coated electrochromic deviceis ready for further manufacturing steps, such as manufacturing windows,mirrors, sunglasses and other devices. The annealed protective polymericcoating is characterized by its transparent, high optical qualities. Thepolymeric coating maintains its protective and optical qualities atleast in a temperature range from about -50° C. to about 150° C., doesnot chemically effect the electrochromic cell layers and has a lowemissivity. The protective coating minimizes the amount of water andoxygen that is capable of passing through to the electrochromic celllayers, and encapsulates the moisture originally present in, andnecessary for, the proper functioning of the electrochromic device.

The thickness of the protective layer does not effect the performance ofthe protective layer; the protective coating can be of any thickness.However, depending on the particular design of an electrochromic deviceand its future application, differentiation of the thickness may provideadditional mechanical protection, environmental protection or bothmechanical and environmental protection. For example, in certainelectrochromic device designs and applications, the thickness of theprotective layer can be up to about 100 microns and in a preferredembodiment, the protective coating comprises sufficient mechanical andenvironmental durability at a thickness in the range between about 0.1to about 20 micrometers.

It should be noted that the protective coatings disclosed herein canalso be used to protect other types of devices and coatings and areespecially useful to those devices that are sensitive to mechanical andenvironmental exposure. The polymeric coating materials can further beused with any device where sealing, protection, and encapsulation ofdevices, structures and coatings is needed to prevent thermally andenvironmentally induced degradation. The coatings are applied to otherdevices in the same manner as applied to electrochromic devices.

PACKAGING ELECTROCHROMIC DEVICES

As mentioned above, because of their sensitive chemical and mechanicalnature, electrochromic devices must be protected from the environment.For example, even small amounts of water, the touch of a finger,cleaning solvents or excess movement can destroy the electrochromicdevice. Even though the polymeric protective coatings in the presentinvention provide excellent protection from mechanical stress andchemical elements, for the electrochromic device to be capable ofwithstanding uses in everyday applications, such as architecturalwindows and eyeglasses, it is necessary to further package the sealedelectrochromic device between rigid, protective substrates (i.e., glass,plastic, or the like).

Solid state electrochromic devices are typically deposited on a firstrigid substrate. The problem is that, until the present invention, noadequate means of adding another rigid substrate (i.e., packaging) totransparent solid state electrochromic devices has been found. It is afeature of the present invention to provide a solid state electrochromicdevice that is capable of being packaged between two protectivesubstrates to provide a packaged electrochromic device sturdy enough forpractical applications.

The protective polymeric coating in the present invention providesadequate protection for electrochromic devices to allow solid stateelectrochromic devices to be packaged. Because of their sensitivenature, unprotected electrochromic devices are poisoned by laminatingmaterials and are, thus, incapable of being packaged. However, anelectrochromic device having a protective coating is protected from anyadverse interactions stemming from the laminate material and anyimpurities that may leech from the laminate materials during thepackaging process.

FIG. 7 illustrates a packaged electrochromic device 70, comprising anelectrochromic device 72 having a second substrate (or laminate) 48, onthe electrochromic device. Electrochromic device 72 comprises anelectrochromic cell 52 having a protective coating 46 on theelectrochromic cell. Electrochromic device 72 has a top portion and abottom portion. The electrochromic cell preferably comprises a firstsubstrate 44 on the bottom portion of the electrochromic device, anelectron conducting layer 30 on the first substrate, a counter electrodelayer 32 on the electron conducting layer, an ion conducting layer 34 onthe counter electrode layer 32, an electrochromic layer 36 on the ionconducting layer, and a second electron conducting layer 38 onelectrochromic layer 36. Protective coating 46 covers the electrochromiccell to form the electrochromic device.

The electrochromic device is packaged by adhering a substrate, orlaminating a laminate to the top portion 74 of the electrochromic device72. Any method of packaging can be used to package an electrochromicdevice having a protective covering, including but not limited to,vacuum bag lamination, low pressure lamination, such as used in thephotovoltaic industry, and the deposition of a hard no-scratch coating.

The problem traditionally encountered with vacuum bag laminationpackaging of solid state electrochromic cells is that solid stateelectrochromic cells are extremely sensitive both physically andchemically. However, in the present invention, the protective polymericcoating 46 on the electrochromic cell 52 protects the electrochromiccell from physical and chemical damage during packaging processes, toallow the electrochromic device to be safely packaged. The protectivecoating 46 allows a laminate material to be applied to theelectrochromic device so that a second substrate can be adhered to theelectrochromic device resulting in a packaged solid state electrochromicdevice 70.

In the vacuum bag lamination process of an electrochromic device, alaminate material 76 is applied to the electrochromic device having aprotective coating. A second substrate, such as glass 48, is thenaligned with an electrochromic device 72 comprising a protectivecoating, wherein the protective coating 46 is adjacent to and in contactwith the laminate 76 and the laminate acts as an adhesive for the secondsubstrate 48. The electrochromic device/second substrate sandwich 70 isplaced into a sealed bag and the air is pumped out of the bag using avacuum, so that the electrochromic device and the second substrate arein mechanical contact having as few air bubbles as possibletherebetween. The bag containing the electrochromic device/secondsubstrate sandwich, is then placed into an autoclave having an elevatedtemperature, i.e., 100° C., and an elevated pressure, i.e., 10atmospheres. At high temperatures and high pressures, the laminatematerial 76 becomes soft and tacky so that the laminate material canfunction as an adhesive. Upon cooling, the laminate material 76resolidifies to adhere the second substrate 48 to the top portion 74 ofthe electrochromic device 72 to form a packaged electrochromic device 70having a first substrate 44 adhered to indium tin oxide layer 30 and asecond substrate 48 adhered to indium tin oxide layer 38.

Unprotected (i.e., uncoated) solid state electrochromic cells have alsobeen too fragile to undergo packaging using photovoltaic lamination.However, when a protective coating is present on the electrochromiccell, the electrochromic device is able to be packaged using lowpressure lamination such as used in the photovoltaic industry.

The low pressure lamination of electrochromic devices comprises: 1)aligning a second substrate 48 with an electrochromic device 72 having aprotective coating 48 thereon; 2)the electrochromic device/secondsubstrate is subjected to a vacuum to remove air trapped between thesecond substrate 48 and the electrochromic device 72; and 3) pressure isapplied to the second substrate 48 while the electrochromicdevice/second substrate sandwich is exposed to heat, to enhance thecontact between substrate 48 and electrochromic device 50. Upon heating,the laminate material 76 becomes soft and tacky and causes the secondsubstrate to adhere to the electrochromic device. The electrochromicdevice/second substrate sandwich 70 is then cooled to solidify thelaminate material 76, which acts as a transparent adhering materialbetween substrate 48 and electrochromic device 72.

Likewise, until the present invention, solid state devices have not beenable to withstand packaging with the deposition of a hard no-scratchcoating. The hard no-scratch coating is preferably a polysiloxane thatadheres extremely well to the protective polymeric coating 48. After thepolysiloxane material is deposited on to the surface of theelectrochromic device using conventional deposition techniques, thedeposited polysiloxane is subjected to a curing process at hightemperatures, i.e., between about 100° C. and 150° C.

It should be noted that the protective coatings disclosed herein canalso be used to protect other types of devices and coatings and areespecially useful to those devices that are sensitive to mechanical andenvironmental exposure. The polymeric coating materials can further beused with any device where sealing, protection, and encapsulation ofdevices, structures and coatings is needed to prevent thermally andenvironmentally induced degradation. The coatings are applied to otherdevices in the same manner as applied to electrochromic devices.

EXAMPLE 1

As illustrated in FIG. 3, once the electrochromic device is coated withthe polymeric protective coating, the long-term performance of theelectrochromic device is improved. FIG. 3 provides a graph illustratingthe percent transmittance and optical density of a polymer coatedelectrochromic device over numerous coloring cycles. The transmittanceof a polymeric coated electrochromic device in a bleached state followedover 62,000 coloring cycle is illustrated by plot 60. The opticaldensity of a polymeric coated electrochromic device in a colored stateover a coloring cycle from 0 to 62,000 is illustrated by plot 62. The62,000 switching cycles between the colored and bleached states of theelectrochromic device were accumulated over an 8 month continuousperiod. Plot 60 illustrating the transmittance for the bleached state ofthe electrochromic device is approximately horizonal, indicating that nodeterioration in the optical quality occurred over the 62,000 cycles.Plot 62 illustrating the optical density of the electrochromic deviceover the 62,000 switching cycles is slightly curved, indicating a slightloss in performance of the electrochromic device over the 62,000 colorswitching cycles. This slight loss, however, can be compensated for byincreasing the switching time.

In contrast, unprotected electrochromic devices operated over acomparable period of time show a rapid deterioration in transmittance oftheir bleached state. The reduction in the bleached state transmitted isalso associated with a steep loss in the performance of unsealeddevices. Residual color which effects the device performance is theprobable cause of the steep decay in transmittance of the bleachedstate. Additionally, uncoated electrochromic devices show a pronounceddecay in the optical density in the colored state over a color switchingperiod of about 62,000 cycles. Decay in the optical density is due tothe rapid loss of charge capacity of the counter electrode layer whichresults in a "lighter" dark colored state.

EXAMPLE 2

FIGS. 4a and 4b illustrate the optical deterioration of an uncoatedtransparent electrochromic device (FIG. 4a) operated continuously at 85°C. for about 100 hours, compared with the defect-free appearance of apolymeric coated electrochromic device (FIG. 4b) cycled under the sameconditions. FIGS. 4a and 4b clearly illustrate the prematuredeterioration of electrochromic devices that are not protected by apolymeric coating material. The premature deterioration illustrated inFIG. 4a is caused by exposure to surrounding environmental effects.These environmental effects are avoided by providing an environmentalprotective coating that inhibits moisture, oxygen, chemicals and othercontaminates from contacting the electrochromic cell layers as well asmaintaining the proper moisture and chemical balance within theelectrochromic cell.

EXAMPLE 3

In a preferred embodiment, a polymeric coated electrochromic device wasformed by purifying a necessary quantity of analpha-[1,4-Biphenylyl]-omega-[4-[[4(4-phenylphenoxy)phenyl]phenylphosphinyl]phenoxy]-poly[oxy-1,4phenylene(phenlphosphinylidene)-1,4-phenyleneoxy-1,4-phenyleneoxy-1,4-phenylene[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]-1,4-phenylene(hereinafter "6-P polymer") polymer. A 10% by weight polymeric solutionof the purified 6P polymer was prepared using an appropriate amount ofchlorobenzene. The 10% (by weight) polymeric solution was filtered twiceusing 5.0 micrometer Teflon membrane and then, for final refinement, a0.2 micrometer membrane filter to remove any solid particles. Thepolymeric solution was then out-gassed under a vacuum for 30 minutes toremove any remaining micro-bubbles or dissolved gasses.

An electrochromic cell with bus bars which had been deposited onto aglass substrate was obtained. The bus bars were covered with an adhesivetape so that the bus bars were not coated with the polymeric coatingmaterial. The electrochromic cell was then mounted in the appropriatevacuum chuck of a resist spinner.

The deposition process was started and the polymer solution wasdispersed on the top surface of the electrochromic cell. The polymericsolution was then spread over the entire surface of the electrochromiccell by spinning the electrochromic cell for 10 seconds at 500 rpms. Thespinning rate was increased to 2000 rpms for 60 seconds to coat theelectrochromic cell with the polymer.

After the spin coating step was complete, the coated electrochromicdevice was dried and annealed for about 20 minutes at about 80° C.,during which time the tape which protects the bus bars was removed. Whenthe drying and annealing steps were completed the device was tested foroptical quality and electrochromic performance and was transferred tothe next manufacturing step.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrated andnot restrictive. The scope of the invention is, therefore, indicated bythe appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed and desired to be secured by United States LettersPatent is:
 1. An electrochromic device comprising:an electrochromiccell; and a coating on the electrochromic cell, the coating comprising apolymer having a general formula selected from the group consisting of:##STR8## wherein Ar is selected from the group consisting of: ##STR9##wherein Ar¹ is selected from the group consisting of: ##STR10## whereinn is between 1 and 10; wherein X is 0 or 1; wherein R is selected fromthe group consisting of H, CF₃, C_(n) H_(2n+1), OC_(n) H_(2n+1) andmixtures thereof; and wherein R¹ is selected from the group consistingof H, CF₃, C_(n) H_(2n+1), OC_(n) H_(2n) +1, -phenyl, fluorenyl,naphtalenyl and mixtures thereof.
 2. An electrochromic device as recitedin claim 1, wherein said polymer has the following recurring structuralunit[Poly[2,5-benzoxazolediyl[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]-5,2-benzoxazolediyl-4,4'-phenylether]]n',wherein n' is a integer number.
 3. An electrochromic device as recitedin claim 1, wherein said polymer has the following recurring structuralunit[α-[1,4-Biphenylyl]-ω-[4-[[4-(4-phenylphenoxy)phenyl]phenylphosphinyl]phenoxy]-poly[oxy-1,4-phenylene(phenylphosphinylidene)-1,4-phenyleneoxy-1,4--phenylene-9H-fluoren-9-ylidene-1,4-phenylene]]n',wherein n' is a real number.
 4. An electrochromic device as recited inclaim 1, wherein said polymer has the following recurring structuralunit [α-[1,4-Biphenylyl]-ω-[4-[[4-(4-phenylphenoxy)phenyl]phenylphosphinyl]phenoxy]-poly[oxy-1,4-phenylene(phenylphosphinylidene)-1,4-phenyleneoxy-1,4-phenylene[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]-1,4-phenylene]]n',wherein n' is a real number.
 5. An electrochromic device as recited inclaim 1, wherein the electrochromic device is a transparentelectrochromic device.
 6. An electrochromic device as recited in claim1, wherein the electrochromic device is a mirror.
 7. An electrochromicdevice as recited in claim 1, wherein the electrochromic device has alow emissivity.
 8. An electrochromic device as recited in claim 1,wherein the coating has a thickness in a range from about 0.1 to about100 micrometers.
 9. An electrochromic device as recited in claim 1,wherein the coating has a thickness in a range from about 0.1 to about20 micrometers.
 10. An electrochromic device as recited in claim 1,wherein the electrochromic cell comprises an electrochromic layer, anion conducting layer and a counter electrode layer.
 11. Anelectrochromic device as recited in claim 1, wherein the coating isthermally stable in a range between about -50° C. and about 150° C. 12.An electrochromic device as recited in claim 1, wherein theelectrochromic device comprises a top portion and a bottom portion, andwherein the electrochromic device comprises a first substrate on thebottom portion;wherein the electrochromic device further comprises asecond substrate on the top portion of the electrochromic device.
 13. Anelectrochromic device as recited in claim 12, wherein the secondsubstrate is a glass substrate.
 14. A process for protecting anelectrochromic device from environmental and mechanical damagecomprising:providing an electrochromic cell; and coating theelectrochromic cell with a polymer having the general formula selectedfrom the group consisting of: ##STR11## wherein Ar is selected from thegroup consisting of: ##STR12## wherein Ar¹ is selected from the groupconsisting of: ##STR13## wherein n is between 1 and 10; wherein X is 0or 1; wherein R is selected from the group consisting of H, CF₃, C_(n)H_(2n+1), OC_(n) H_(2n+1) and mixtures thereof; and wherein R¹ isselected from the group consisting of H, CF₃, C_(n) H_(2n+1), OC_(n)H_(2n+1), -phenyl, fluorenyl, naphtalenyl and mixtures thereof.
 15. Aprocess for protecting an electrochromic device from environmental andmechanical damage as recited in claim 14, further comprising annealingthe coating on the electrochromic cell by heating the electrochromicdevice to a temperature above about 65° C.